It was my turn to make move 22. I think, with perfect play, I was lost. I also think that after move 25, I was won. It was a different sort of ending than I've played before.

I don't get move 24… red should have made the chain longer it seems and win the game.

You are right in both assumptions, Dvd. In this position there is a very long chain, so whoever wins the chain fight wins the game, and it is impossible to prevent a chain in the 3×3 area in the upper left. However, red's 25th move is losing, since it fails to force a chain. For example b5-b6 instead of b4-b5 would have won.